13,860 research outputs found
The effect of tyres and a rubber track at high axle loads on soil compaction-Part 2: Multi-axle machine studies
This paper reports on a study of the effect of the passage of multi-axle harvesting machines on the soil physical properties. In particular, it investigates the effect of the rear tyre of a combine harvester on the amount of soil compaction subsequent to the passage of the front tyre/track. The work was conducted in controlled laboratory conditions to determine the effect of a simulated self-propelled combine harvester with a total machine weight of 30–33 t. This was assessed by embedding talcum powder tracer lines in the soil to measure soil displacement and soil density changes. Dry bulk density and penetrometer resistance were also measured. The results showed that the benefit of the rubber track found by Ansorge and Godwin [2007a. The effect of tyres and a rubber track at high axle loads on soil compaction: Part 1: Single Axle Studies. Biosystems Engineering 98 (1), 115–126] was maintained after the additional passage of the rear tyre. After the passage of a track the effect of rear tyre size was insignificant, but the rear tyre size had a significant influence on soil density when following a leading tyre. This was due to a higher strength layer at the soil surface created by the track which was able to withstand the load of the subsequent passes and protect the soil below from further compaction. Results similar to those found for a tracked machine were also achieved by three passes of a 900 mm section width tyre at 5 t load and 0.5 bar inflation pressure. The track results for the 33 t machine were very similar to those of a smaller combine harvester with a total load of 11 t and similar rut width. The study confirmed the benefit of tracks with regard to soil compaction and emphasised the fact that total axle loads and machine weights are less important than how the loads are distributed to the soil
Two-sided Certification: The market for Rating Agencies
Certifiers contribute to the sound functioning of markets by reducing a symmetric information. They, however, have been heavily criticized during the 2008-09 financial crisis. This paper investigates on which side of the market a monopolistic profit-maximizing certifier offers his service. If the seller demands a rating, the certifier announces the product quality publicly, whereas if the buyer requests a rating it remains his private information. The model shows that the certifier offers his service to sellers and buyers to maximize his own profit with a higher share from the sellers. Overall, certifiers increase welfare in specific markets. Revenue shifts due to the financial crisis are also explained
Distance to U Pegasi by the DDE Algorithm
A distance is found for the W UMa type binary U Pegasi, with a newly modified
version of the Wilson-Devinney program (W-D) that makes use of the direct
distance estimation (DDE) algorithm. The reported distance of d = 123.6pc is an
average based on solutions for B and V data and a primary star temperature of
5800K. Standardized light curves (not differential), radial velocities, and a
spectroscopic primary star temperature are input to the pro- gram. Differential
corrections were performed for each light curve band along with the velocities
for two primary temperatures that span 100K. Log10d is a model parameter like
many others that are adjustable in W-D. The eclipsing binary distance agrees
with the Hipparcos parallax distance and is more precise.Comment: 2 pages, 1 table, International Conference: Binaries - Key to
Comprehension of the Universe, Brno, Czech Republic June 8-12, 200
Photon-Photon Interactions in Dynamically Coupled Cavities
We study theoretically the interaction between two photons in a nonlinear
cavity. The photons are loaded into the cavity via a method we propose here, in
which the input/output coupling of the cavity is effectively controlled via a
tunable coupling to a second cavity mode that is itself strongly
output-coupled. Incoming photon wave packets can be loaded into the cavity with
high fidelity when the timescale of the control is smaller than the duration of
the wave packets. Dynamically coupled cavities can be used to avoid limitations
in the photon-photon interaction time set by the delay-bandwidth product of
passive cavities. Additionally, they enable the elimination of wave packet
distortions caused by dispersive cavity transmission and reflection. We
consider three kinds of nonlinearities, those arising from
and materials and
that due to an interaction with a two-level emitter. To analyze the input and
output of few-photon wave packets we use a Schr\"odinger-picture formalism in
which travelling-wave fields are discretized into infinitesimal time-bins. We
suggest that dynamically coupled cavities provide a very useful tool for
improving the performance of quantum devices relying on cavity-enhanced
light-matter interactions such as single-photon sources and atom-like quantum
memories with photon interfaces. As an example, we present simulation results
showing that high fidelity two-qubit entangling gates may be constructed using
any of the considered nonlinear interactions
Two-sided Certification: The market for Rating Agencies
Certifiers contribute to the sound functioning of markets by reducing asymmetric information. They, however, have been heavily criticized during the 2008-09 financial crisis. This paper investigates on which side of the market a monopolistic profit-maximizing certifier offers his service. If the seller demands a rating, the certifier announces the product quality publicly, whereas if the buyer requests a rating it remains his private information. The model shows that the certifier offers his service to sellers and buyers to maximize his own profit with a higher share from the sellers. Overall, certifiers increase welfare in specific markets. Revenue shifts due to the financial crisis are also explained.Certification, Rating Agencies, Asymmetric Information, Financial Markets
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